1. Field of the Invention
The present invention is directed to an antenna assembly, and is more particularly directed to a ground-based antenna assembly.
2. Background Information
In recent years, the telecommunications industry has seen the development and deployment of commercial non-geostationary orbit (NGSO) communication systems. These NGSO communication systems form a network of nodes that deliver a variety of interactive services to residential, commercial and government subscribers at a cost that is substantially less than previously available. However, in order to provide satisfactory performance under most, but not necessarily all operating conditions, a ground-based antenna is needed that will provide transmission and/or reception capabilities at residential, commercial or governmental locations under the unique operating conditions presented by a NGSO communication system and many other communication system configurations.
For example, due to the relatively rapid speeds in which the satellites in an NGSO communication system move over the surface of an underlying celestial body, such as the Earth, each NGSO satellite is visible to particular user locations for relatively small increments of time. Therefore, the ground-based antenna associated with a particular subscriber location must be able to support a hand-off process that involves switching communication services between cells or beams of a single satellite footprint and/or between cells or beams of different satellites within the NGSO communication system. This support of the hand-off process by the ground-based antenna is generally enhanced if maximum hemispherical coverage is available (i.e., a 360-degree azimuth field-of-view from horizon to zenith).
One prior art ground-based antenna that provides substantial hemispherical coverage is a mechanically positioned dish antenna. However, as may be appreciated, the minimization of moving components in an antenna is preferred as this minimization increases reliability and decreases mechanically generated noise and vibration. A mechanically non-moving alternative to the mechanically positioned dish antenna is the electronically scanned phased array antenna. While reliability is increased and mechanically generated noise is decreased due to a substantial reduction of mechanical moving parts in a phased array antenna, different concerns arise when a phased array antenna is placed at a subscriber location.
Generally, phased array antenna apertures have a scanning range that is limited to 55-60 degrees off the mechanical boresight (i.e., the normal to the aperture plane). Therefore, if the 360-degree field-of-view from horizon to zenith is sought, multiple phased array antenna apertures must be used to form an antenna assembly that will provide this area coverage. In addition, as the frequency band allocated for the communication system uplink is generally different than the frequency band for the communication system downlink, and also significantly separated in frequency, separate antenna apertures are typically needed in a phased array antenna assembly. Furthermore, as a relatively high antenna gain is preferred to enhance the uplink and downlink in the communication system, the diameters of the phased array antenna apertures are relatively large. Therefore, in order to provide the aforementioned field-of-view, a number of large diameter transmit apertures and a number of large diameter receive apertures may be required and the complete antenna assembly may have a large size. As a large antenna assembly size in a residential, commercial or governmental user setting is aesthetically and economically undesirable, size reduction in a phased array antenna assembly is advantageous.
Accordingly, a ground based antenna assembly for use in communication with a plurality of satellites is desired that has a reduced number of mechanically moving parts and a overall size that is minimized. Furthermore, additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.
In accordance with the teachings of the present invention, a ground-based antenna assembly is disclosed herein. The ground-based antenna assembly includes an assembly base defining a plane and plurality of receiving panels having a first conic shape. The plurality of receiving panels are radially-spaced a first radial distance about the assembly base and tilted at a first angle with respect to the plane for a receiving field-of-view. The ground-based antenna also includes a plurality of transmitting panels having a second conic shape. The plurality of transmitting panels are radially-spaced a second radial distance about the assembly base and tilted at a second angle with respect to the plane for a transmitting field-of-view. In addition, the plurality of transmitting panels are radially offset and nested with respect to the plurality of receiving panels.